Talks on Iran's nuclear program ended today in Geneva. The outcome? Inconclusive but hopeful. Negotiators agreed that Iran has put forward an important proposal that needs to be fleshed out.

As NPR's Peter Kenyon reports, all eyes turn now to another round of talks early next month.

PETER KENYON, BYLINE: There were no new restrictions on Iran's nuclear program to announce and no lifting of sanctions, either. But officials from Iran and six world powers say there appears to be a new willingness to get to a diplomatic solution, and both sides agree that momentum shouldn't be lost.

Summing up two days of talks that she calls the most detailed we've ever had, by a long way, the lead international negotiator Catherine Ashton says a lot of work lies ahead, but there's reason to keep talking, based on Iran's presentation here this week.

CATHERINE ASHTON: The Foreign Minister of the Islamic Republic of Iran presented an outline of a plan as a proposed basis for negotiation, which is being carefully considered as an important contribution.

KENYON: That was part of a joint statement agreed by the two sides, another first for these talks. For only the second time, the U.S. and Iranian delegations met in a bilateral meeting. And the group sessions proceeded at a much faster pace thanks to the willingness of the top Iranian officials to use their fluent English.

Iranian Foreign Minister Mohammad Javad-Zarif, who led the delegation despite severe back pain, joined Ashton in refraining from sharing any details of the negotiations. But he did address one issue, the so-called additional protocols of the U.N. nuclear agency, which sends inspectors to Iran on a regular basis. These protocols would allow spot inspections on sites not usually on the list of facilities where inspections are allowed. While saying that Iran has not agreed to those protocols, Zarif did say Iran is discussing greater monitoring of its nuclear sites.

MOHAMMAD JAVAD-ZARIF: Well, we are discussing various monitoring mechanisms at this stage, which do not include additional protocol.

KENYON: Saying it's time to look forward, not back, Zarif also made a veiled reference to the U.S. Congress, where even more Iranian sanctions are awaiting a vote. Zarif says he hopes the U.S. won't do anything to exacerbate the problem, which from Iran's point, more sanctions certainly would.

Analyst Michael Adler, with the Wilson Center, says sanctions relief is likely to remain a major obstacle because while Congress held off voting on more sanctions to see what came out of this meeting, the apparent lack of results might trigger a new push to punish Tehran.

MICHAEL ADLER: Does that mean that it's going to take three meetings to get concrete progress? How long will the U.S. Congress have patience as this unfolds?

KENYON: A senior administration official says there may be a closed-door classified briefing for Congress to explain where the two sides are in the process. The official also said U.S. allies, including Israel, will be briefed on the talks. The U.S. view of the situation, the official said, is that the new administration in Iran has created the chance for a new beginning at the negotiating table, but that there's a long way to go.

For now, all the big questions remain unanswered. Will Iran really agree to physically limit the amount of uranium it can enrich? Will it agree to intrusive inspections to verify that it's keeping its word? Could the Obama administration really get Congress to lift the most painful sanctions even if it wanted to?

But analyst Ali Vaez, at the International Crisis Group, says even so, given where the negotiators were starting from, this meeting marks a positive step.

ALI VAEZ: Well, I would say this is progress. You know, the two sides are speaking the same language. They're talking about objectives. They're talking about determining first steps, last steps. And after all these years of misunderstanding and misguided expectations, I think speaking the same language and working off the same draft is progress.

KENYON: Nuclear, scientific and sanctions experts from both sides are expected to meet before the negotiators return here on November 7th for another round.